Express a function - Trigonometic Problem

[okh]

Right Trapezium - Simple Problem Using Trigonometry

Homework Statement

http://img207.imageshack.us/img207/8510/imagejat.jpg
ABCD is a right trapezium. CB = 3 = CD. P is a point of CB. The angle CDP is called x.
I have to express the function
f(x) = DP + CP
and I have to find the interval in which the function can be considered.

Homework Equations

The Attempt at a Solution

I've found the function:
http://img836.imageshack.us/img836/848/imageuox.jpg

But I can't understand how I can find the interval.
Thank you very much for helping!

PS: the solution on my book is 0<=x<=30º.

 

[SammyS]

Homework Statement

http://img207.imageshack.us/img207/8510/imagejat.jpg
ABCD is a right trapezium. CB = 3 = CD. P is a point of CB. The angle CDP is called x.
I have to express the function
f(x) = DP + CP
and I have to find the interval in which the function can be considered.

Homework Equations

The Attempt at a Solution

I've found the function:
http://img836.imageshack.us/img836/848/imageuox.jpg

But I can't understand how I can find the interval.
Thank you very much for helping!

PS: the solution on my book is 0<=x<=30º.

What are the possible values of DP + CP ?

 

[okh]

Uhm.. What do you mean? It depends on which x you choose. The function express that sum, indeed.

 

[scurty]

Uhm.. What do you mean? It depends on which x you choose. The function express that sum, indeed.

There is a minimum value for DP + CP and a maximum value for DP + CP. What is the range of values and how does that relate to choices of x in your equation?